A sidewalk provides space for pedestrians to walk parallel with motor-vehicle traffic without having to walk in the travel lane.
Source: Designing for Pedestrian Safety

Pedestrian Accomodations at Complex Interchanges

There are a variety of pedestrian facilities that should be considered in interchange areas in order to allow pedestrians to walk along streets and/or cross streets at or near interchange ramps. Providing sidewalks or walkways is needed to provide a space for pedestrians to walk parallel with motor-vehicle traffic without having to walk in the travel lane. Where pedestrians need to cross near interchange ramps, it is important to apply some of the same principles that have been discussed earlier for safe intersection design; that is, to the extent practical, intersection crossings should be kept relatively short, with turning radii balanced to meet the needs of pedestrians as well as turning trucks, and raised median islands may be needed.

Signal treatments (traffic and pedestrian signals) are often appropriate at the intersection of ramps on the surface streets, and these can be timed to facilitate safe pedestrian travel, as well. Free-flow vehicle lanes (right-turn slip lanes) should be designed to be pedestrian friendly, in terms of roadway approach angle, marked crosswalk and narrow turn lane. Features should also be provided to accommodate pedestrians with various typed of visual and mobility disabilities. Curb ramps, with tactile warning strips, accessible pedestrian signals, walkways clear of barriers and clutter, well-designed medians are examples of such measures. Also, roadway lighting may be essential for creating a safer pedestrian environment near interchange areas.

The design of the intersections, pedestrian features, and crossing movements will vary widely for different types of interchanges. Some of the types of interchanges which are currently in use include:
• Diamond interchanges
• Cloverleaf interchanges
• Single-point, urban interchange (SPUI)
• Superstreet interchange
• Double divergent diamond interchange

Some of the features of each type of newer interchange types and their measures for accommodating pedestrians are described in the FHWA report Alternative Intersections/Interchanges: Informational Report (AIIR).9

Purpose

One of the most challenging situations facing pedestrians in urban and suburban areas is how to walk safely through areas with interchanges, yet pedestrian travel is often not considered adequately when interchanges are planned and designed. At interchange areas, pedestrians face the task of crossing at the intersection of on-ramps and off-ramps when walking along the local or arterial street. In some situations, pedestrians may also wish to cross the local street near ramps. In either situation, pedestrian crossing activity may conflict with high-speed right-turn or left-turn motorists who are decelerating from the off-ramp or accelerating onto the on-ramp. Pedestrians who attempt to cross the local street may also conflict with through vehicles near the interchange area. Providing pedestrian accommodations for is, therefore, of particular importance in interchange areas.

Considerations

• Pedestrian facilities should be incorporated into the planning and design of interchanges.
• The intersection of freeway ramps and local streets should be designed like other urban intersections in terms of slow vehicle approach speeds, narrow crossing distance, and appropriate signs, signals, and markings.
• Consider a jug-handle design for pedestrian and bicycle improvements.

Estimated Cost

Costs for interchange-related treatments will depend on the specific type of treatment that is being considered. See other countermeasures for costs of various treatments, including signs, signalization, crosswalk markings, sidewalks, or geometric treatments such as roadway narrowing.